Process of producing polycarbonate

ABSTRACT

For carrying out phase boundary surface reactions of components, e.g., production of polycarbonates from phosgene, Bisphenol A, sodium hydroxide and water a reaction tube is used, which comprises a series of residence time sections of relatively large internal tube diameter and alternately positions with respect to mixing sections of smaller internal tube diameter, the mixing sections providing Reynolds numbers greater than 2,000 for the reactants.

nited States Patent Vernaleken et al. 1 July 4, 1972 54 PROCESS OFPRODUCING 2,312,639 3/1943 Gronemeyer -259/4 POLYCARBONATE 2,913,31811/1959 Erasmus et al.... ..23/284 3,119,704 1/1964 Harrell et a1 259/4X 1 Inventors: g Vernaleken, Krefeld; Otto Court, 3,128,993 4/1964Platte et a] ...259 4 Neuss; Kurt Weirauch, Krefeld-Bockum, 3,530,0949/1970 Schnelletal. ..260/47 allofGermany 3,160,606 12/1964 Dietrich eta1 ..260/47 [73] Assignee: Farbenfabriken Bayer Aktiengesellschaft,FOREIGN PATENTS OR APPLICATIONS Leverkusen, Germany 138,592 6/1960U.S.S.R. ..259/4 Aprll 8, 1970 923,192 4/1963 Great Britain....

[21] Appl' 26642 Primary ExaminerSamuel H. Blech Att0rney-Burgess,Dinklage & Sprung [30] Foreign Application Priority Data [57] ABSTRACTAprll 22, 1969 Germany ..P 19 20 302.2

For carrymg out phase boundary surface reactlons of components, e.g.,production of polycarbonates from phosgene, [52] US. Cl 55....260/47 XA,23/252, 23/2705, Bisphnol Sodium hydroxide and water a reaction tube is51 I t Cl C08 17 13 used, wh1ch compnses a senes of resldence tlmesectlons of l I}. g relatively large internal tube diameter andalternately p [58] Field of Search ..23/284, 252, 270.5; 259/4; tionswith respect to mixing Sections of Smaller internal tube 260/47 XAdiameter, the mixing sections providing Reynolds numbers greater than2,000 for the reactants. [56] References Cited 4 Claims, 3 DrawingFigures UNITED STATES PATENTS 2,088,591 8/1937 Ferkel ..259/4 UXPATENTEDJuL 4 m2 FIG] FIG. 3

INVENTORS HUGO VERNALEKEN, OTTO COURT, KURT WEIRAUCH.

PROCESS OF PRODUCING POLYCARBONATE This invention relates to a reactiontube in which phase boundary surface reactions may be continuouslycarried out.

In phase boundary surface reactions, which are characterized by anexchange of substance between two or more phases which are immisciblewith one another, the chemical conversion rate is determined by thereaction velocity and by the reaction time. Continuous operation ofthese reactions often leads to difficulties, since mixing of thereactants occurs in the reaction apparatus, so that separate fractionsof the initial materials emerge prematurely and incompletely reacted,while other fractions remain in the apparatus for a correspondinglylonger period and are subject to undesirable side reactions. The degreeof mixing depends on the arrangement and the shape of the reactionvessels.

Very different examples of reaction vessels are the perfectly mixingstirrer-type vessel and the reaction tube. With a continuousthroughflow, a narrow residence spectrum is obtained in a long reactiontube, while the said spectrum is broad in the perfectly mixingstirrer-type vessel. In order to carry out twophase reactions in areaction tube, high Reynolds numbers and thus high flow velocities arerequired in order to produce a thorough mixing of the phases. This isobtained in long tubes with a small diameter, but a large pressure losshas to be accepted. For many reactions which require relatively longresidence times, the unfavorable ratio between length and diameter inreaction tubes is found to be uneconomical on account of the pressureloss. For reaction of this type the stirrertype vessel is chosen.However when a narrow residence time distribution is required, it isnecessary for a large number of such vessels to be arranged in series. I

The present invention obviates the defects of the known arrangements byan alternating sequence of residence time sections having relativelylarge internal tube diameters and mixing sections of relatively smallintemal tube diameters, the latter sections guaranteeing Reynoldsnumbers greater than 2,000.

In this way, the disadvantages, such as high pressure loss in thereaction tube and a large number of series-connected stirrer-typevessels, are avoided.

In order to ensure a satisfactory reaction, the invention advantageouslyprovides a combination of at least three residence time sections andthree mixing sections.

According to one particular embodiment of the arrangement of the presentinvention, the ratios between the tube diameters of the residence timesections and the mixing sections vary between 3 and 50 and the ratio oftheir lengths may vary between I and 50.

The tube diameters of the mixing sections are chosen to be so large thatflow velocities in these sections correspond to Reynolds numbers ofadvantageously greater than 2,000, but preferably greater than 2,300.During the passage of the reactants through the mixing tubes, a stableemulsion is formed. This emulsion then passes to the residence timetubes, the diameters of these tubes being such that the flow velocity insaid tubes is such that no separation of the reactants into componentparts occurs and good substance exchange takes place.

These arrangements are also suitable for carrying outreactions in thepresence of solid catalyst substances in powder form, which substancestend to settle.

Examples of uses for this process are the production of polycarbonate bythe phase boundary surface process, emulsion polymerization of vinylmonomers and fat saponification with aqueous alkali.

A reaction tube consists, for example, of 19 mixing tubes, with anominal diameter of 4 mm and a length of mm, and 19 residence time tubeswith a nominal diameter of 20 mm and a length of 1,300 mm.

An initial material for reaction, consisting of 60 mols of phosgene inliters of methylene chloride and 50 mols of Bisphenol A and mols ofsodium hydroxide solution, together with l.4 mols of p-tert.-butylphenol and 0.25 mols of triethylamine, in 80 kg of water, were conductedthrough this apparatus per hour.

A polycarbonate with a relative viscosity of 1.34, measured in methylenechloride at 25 C with a concentration of 0.5 g in 100 ml, was obtained.The polycarbonate had no saponifiable chlorine.

One embodiment of the reaction tube according to the invention is shownby way of example and is more fully explained by reference to theaccompanying drawing, wherein:

FIG. 1 is a diagrammatic view showing a construction for a reaction tubeof the present invention.

FIG. 2 is a similar view showing a sinuous construction of the reactiontube, and

FIG. 3 is a cross sectional view showing one particular constructionalform with fitting sleeves.

In FIG. 1, a reaction mixture is pumped from a storage vessel l by wayof a proportioning pump 2 to a reaction tube 3. The reaction tube 3consists of residence time sections 4 and mixing sections, in which aReynolds number greater than 2,300 is achieved. By means of openings 6,other reactants can be admixed or samples can be taken.

In FIG. 2, residence time sections 14 are arranged in juxtaposition,while mixing sections are constructed as connecting arcuate sections 15.

In FIG. 3, sleeves 24 and apertured discs 25 are fitted into a tube 20,the said sleeves representing the residence time sections and the discsrepresenting the mixing sections.

We claim:

1. Process for continuously producing a polycarbonate by reaction ofmaterial in at least two phases and comprising phosgene, Bisphenol A,sodium hydroxide and water, which comprises passing the material thougha series of residence time sections of relatively large cross-sectionalarea, and a series of mixing sections each composed of a tube ofrelatively small cross-sectional area, the residence time sections andand mixing sections alternating in position with the mixing sectionscommunicating adjacent residence time sections for flow of saidmaterials serially though said sections, the Reynolds number in themixing sections being greater than 2,000, whereby said phases andintermixed in the mixing sections to form emulsions, and react in theresidence time sections to form the polycarbonate.

2. Process according to claim 1, the emulsions passing through theresidence time sections without separation.

3. Process according to claim I, said Reynolds number being greater than2,300.

4. Process according to claim 1, said material including methylenechloride, p-tert. butylphenol, and triethylamine.

UNITED STATES PATENT OFFICE CERTIFICATE OF CRECTKON Patent No. DatedJuly 4, 1972 Inventoflg) Hugo Vernaleken et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Col, 2 line 47; cancel "and" (second occurrence).

Col. 2, line 52, after "said phases" change "and" to "are".

Signed and sealed this 17th day or October 1972.

(SEAL) Attest:

EDWARD M.FLETGHER,JR. ROBERT, GOTTSCHALK Commissioner of PatentsAttesting Officer

2. Process according to claim 1, the emulsions passing through theresidence time sections without separation.
 3. Process according toclaim 1, said Reynolds number being greater than 2,300.
 4. Processaccording to claIm 1, said material including methylene chloride,p-tert. butylphenol, and triethylamine.